Americans only use city water to flush toilets and water plants. The only place I can think of that has good tap water is San Francisco. Here in Los Angeles it's probably worst in the nation. We use bottled water for everything. It's ok, health-wise, to drink the tap water, it only tastes like poison.

I'm surprised that the restaurant served you untreated water. That's rare around here, most places have an RO system so the water they serve is ok.